I've been thinking of adding a folding handle bar stem similar to what savarin did here,

In trolling the bins at the recycling yard, I came across this, made from stainless .
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Don't know what it was made for, but it looks just about perfect at .75" in dia. & 6" long to use for my version of a foldable stem. My idea is to weld this into the stem & have a section of tubing covering the joint so it doesn't flex during riding,
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but be able to slide it up to allow the joint to flex when you want to get on & off the bike. May also add a spring to keep it in place. Will let you know how it goes.